This invention relates to the provision of lateral support for xe2x80x9cfloating wallsxe2x80x9d above a floating concrete slab.
Expansive or swelling soils are present at many locations across the United States and around the world. Expansive soils expand when the water content of the soil increases. Expansive soils create the greater problems when they are present in semi-arid climates where a water deficit normally exist prior to the development of residential communities.
When a residential community is built in an area of expansive soils, the soil environment is dramatically changed. Much of the ground surface, which was previously open to the atmosphere, is covered by houses, driveways, streets and sidewalks. These pavements and strictures limit the amount of moisture that can evaporate from the ground. Additionally, homeowners typically plant a grass yard or create other landscaping that requires irrigation during the summer season. For example, it is not uncommon for homeowners in semi-arid climates, which normally receive less than 20 inches of annual precipitation, to add an additional 40 to 60 inches of water to their lawns during the summer season.
This combination of covering the soil, which reduces natural evaporation, and adding additional irrigation water, combined with the tendency of normally dry soils to draw the water below the surface before it can evaporate greatly increases the moisture levels in the soil below buildings. The increased soil moisture causes the soil to swell or heave upward. As the expansive soils swell, they exert upward forces on surface structures such as streets, buried utilities and, most significantly, concrete slab floors. These lifting forces are powerful enough to actually lift such surface structures.
To accommodate upward heaving of basement slab-on-grade floor, building codes typically require the use of slip joints between the basement slab and the foundation walls of a house to allow the basement slab to rise and fall relative to the foundation walls. The foundation walls are supported on caissons that are preferably anchored to bedrock below the level of soil wetting to make the walls immune to swelling soils. Thus, the slip joints provide tolerance for swelling soils and allow the slab to xe2x80x9cfloatxe2x80x9d.
Because the slip joints allow the concrete slab to rise and fall as the moisture content of the under lying soil varies, any walls constructed immediately above the floating slab must be constructed in such a manner that when the slabs rise the walls are not deformed or crushed between the concrete slab and the house above. Building codes typically require that all walls constructed on concrete floors that are designed as xe2x80x9cfloating slabsxe2x80x9d also be xe2x80x9cfloated.xe2x80x9d
A xe2x80x9cfloating wallxe2x80x9d is typically constructed of vertical studs that are secured only to the joists of the floor above with a gap between the lower end of the wall and the floor. Because the floor joists are typically supported by the concrete foundation walls which are anchored to bedrock below the level of the expansive soil, they do not rise or fall with the floating slab. As the floor rises and falls, the gap between the wall lower end and the slab will narrow and widen correspondingly.
Since a xe2x80x9cfloatingxe2x80x9d wall has no vertical support at its base, the bottom of the floating wall must be stabilized against lateral movement. Typically, a nail is driven through a hole (having a diameter greater that the nail) in the bottom plate of the wall and into a plate fastened to the floating wall. As the slab rises and falls, the nail will slide upward and downward in the bottom plate hole, while resisting, to a degree, sideways forces exerted against the wall.
While this arrangement is generally accepted under local building codes, the lateral support provided is minimal and any significant lateral force applied to the floating wall will cause the wall to deflect, resulting in damage to the floating wall.
Wall construction techniques have been developed to accommodate seismic movement, such as that disclosed by Rasmussen in U.S. Pat. No. 3,861,103 and by Gilmour in U.S. Pat. No. 5,040,345, neither of these has application to a stud wall hung from joists above a floating slab.
Thus, there is a continuing need for improved need for improved lateral support system for walls hung above a floating slab that are inexpensive, easily installed and have greater resistance to lateral forces.
The above-noted problems, and others, are overcome by a device for providing lateral support to the base of a wall hung over a floating slab, which comprises an elongated fitting having at least one longitudinal tube, each for receiving a nail having a length greater than the longitudinal tube, a bracket having an opening for receiving the elongated fitting in a slidable relationship parallel to said nail, means for securing the bracket to a bottom plate in a hanging wall adjacent to the bottom of the hanging wall so that said nails may be driven downwardly into an adjacent baseplate secured to a floating slab.
For maximum lateral support, two parallel longitudinal tubes and two nails are preferred. While additional nails may be used, the slightly greater lateral support is generally not sufficient to justify the additional cost, complexity and difficulty in driving closely adjacent nails.
Although the bracket can be fastened to the bottom plate in any suitable manner, a flange extending generally perpendicular to the bracket at the nail head end with means to fasten the flange to the bottom plate with the longitudinal tube(s) extending through the bottom plate provides optimum strength and ease of installation.